The present invention relates to a power transmission control device, a power transmission device, an electronic instrument, a non-contact power transmission system, and the like.
In recent years, non-contact power transmission (contactless power transmission) that utilizes electromagnetic induction to enable power transmission without metal-to-metal contact has attracted attention. As application examples of non-contact power transmission, charging a portable telephone, charring a household appliance (e.g., cordless telephone handset), and the like have been proposed.
JP-A-2006-60909 discloses related-art non-contact power transmission. According to the technology disclosed in JP-A-2006-60909, a power transmission device (primary-side instrument) monitors the peak value of an induced voltage signal of a primary coil, and compares the peak value with a given threshold voltage to detect the power-reception-side load state, whereby a metal foreign object is detected.
According to the technology disclosed in JP-A-2006-60909, the drive frequency of the coil is set at a constant value. Therefore, the foreign object detection accuracy cannot be improved to a satisfactory level.